1. Field of the Invention
This invention relates generally to threaded fasteners, such as bolts, and, more particularly, to an anti-rotation locking assembly for a threaded bolt with hexagonal wrenching recess which has particular use in mounting an exhaust manifold or modified exhaust pipes to the block of an automotive engine where there is very little clearance between the projected surface of the exhaust pipe and the head of the bolt.
2. Disclosure of the Relevant Known Prior Art
A number of techniques have been described to prevent bolts from working loose due to vibration. For example, in U.S. Pat. No. 4,734,001 (1988), Bennett discloses a threaded fastener with detachable locking plate of generally teardrop shape axially retained on the head of a bolt by an E clip whereby the plate prevents rotation of the bolt by abutting a stationary object. The problem with Bennett's invention for use on automotive exhaust manifolds and exhaust pipes is that there is generally not enough clearance between the projected surface of the exhaust pipe and the head of the bolt to accommodate Bennett's locking plate because the locking plate surrounds the head of the bolt and thus increases its diameter.
In U.S. Pat. No. 4,185,937 (1980), Anderson discloses a bolt with cylindrical threaded portion and integrally connected to an enlarged circular headed portion with hexagonal wrenching recess and elastically deformable annular ring spaced apart from the enlarged head portion, co-axially therewith, and secured thereto by axially extending connecting fingers. Although Anderson's device is applicable to limited access environments, such as turbine engines, it would be extremely impractical to use his fastener on exhaust manifolds primarily due to the lack of a suitable tool for deforming the annular ring to accommodate the shape of each exhaust pipe it engages.
Other fasteners are similarly described in the prior art, but none are known for use in automotive exhaust manifolds.